Electrochromic devices that are applied to light control devices and display devices use a phenomenon called electrochromism that, when voltage is applied, reversible oxidation-reduction reaction occurs, which leads to reversible coloration or discoloration. The electrochromic device is commonly composed of, for example, a device in which a transparent electrode substrate, an electrochromic layer, and a counter electrode substrate are sequentially provided.
Until now, as a compound having the electrochromic characteristics, for example, inorganic compounds such as tungsten oxide have been known (Patent Document 1), and a method in which a film of the inorganic oxide is formed on a transparent electrode by vacuum deposition method or sputtering method to manufacture an electrochromic device has been developed. However, the manufacturing method has a problem that vacuum technique is essential when forming the film and thus the cost increases.
As a device that can be manufactured at a lower cost and simpler manufacturing process, for example, various electrochromic devices using organic electrochromic compounds and the like including viologen derivatives and the like have been developed.
For example, viologen compounds for green electrochromic displays (Patent Document 2), electrochromic mirrors using polymer compounds having a viologen structure (Patent Document 3), and electrochromic devices including an electrolyte layer that is obtained by copolymerization of a precursor component of a solid polyelectrolyte and a reactive viologen compound (Patent Document 4) have been developed.
Furthermore, applications of hyperbranched polymers to electrochromic devices have been developed, and examples of them include triazine ring-containing multibranched polymers that exhibit electrochromic characteristics by doping of positive ions (Patent Document 5) and electrochromic devices that include, on the outer peripheral parts, a layer containing core-shell microspheres having a functional layer consisting of functional groups with an electrochromic function (the microspheres are, for example, dendrimers or hyperbranched polymers) (Patent Document 6).